That means—just as the AP Stylebook did in its tweet—you can begin sentences with “hopefully,” which is an adverb, and insulate yourself against attacks from the grammar police. “The AP Stylebook says it’s A-OK,” you can tell them.

Many (or maybe most) of you were probably letting “hopefully” slip in your conversation and maybe even your prose. For instance: “Hopefully, I will remember to tell the editors in my life about this change from the AP.” Technically, that’s incorrect. Mignon Fogarty, a.k.a. Grammar Girl, explained the rule:

“The traditional use of hopefully, which goes back to at least the 1600s, is to mean ‘in a hopeful manner,’ as in Squiggly looked hopefully at the box of chocolates.”

In Grammar Girl’s example, “hopefully” is an adverb that modifies “looked,” so Squiggly is looking at the chocolates in a hopeful manner.

“But about 300 years later,” Grammar Girl continued. “People started using hopefully to mean ‘I hope,’ as in Hopefully, I'll get some of that chocolate.”

For the record, Fogarty is OK with people using “hopefully” to start a sentence. “This is another great change by the AP because it reflects how people already use and understand 'hopefully,'” she told PR Daily via email. “I've been hopeful for years that 'hopefully' would get this kind of style guide support.”

Other writers and editors are less forgiving than Fogarty.

On the blog JimRomenesko.com, a number of commenters mourned the change. “When enough people fail to learn the rule, the mistake becomes the rule. This is change but not progress,” said one commenter.

Twitter users voiced their displeasure as well. One person questioned whether it was a late April Fools’ Day joke. Another person added: “Really wish you hadn't done this. But I understand why. It's like media as a plural word—you can't fight the tide forever.”

Rob Reinalda, the executive editor at Ragan Communications (which publishes PR Daily), called this another example of people writing like they talk.

“It's lazy and it's subjective,” he said. “The speaker presumes that everyone shares that hope. Do I use it in casual conversation? Yes, but I leave it out of my writing.”

Reinalda said his speaking audience is usually a few people, and they share a common purpose or worldview.

“I hope that (not hopefully...) my readership is extensive and diverse,” he added. “Let them have their own hopes; I just want to offer tips on syntax and usage.”

You can read some of Reinalda’s tips on language—as well as a brief rant or two—on Twitter. He’s @word_czar.